Interpretive Summary: In the Unites States, much of the more than 5 billion kg of wheat bran produced each year are used for animal feed. Conversion of this byproduct of wheat flour milling to products of higher commercial value would be extremely important to the wheat industry. To this end, much research has been devoted to chemical and physical treatments designed to harvest a certain class of indigestible carbohydrates, termed feruloylated arabinoxylooligosaccharides (AXOS), from wheat bran. These AXOS may confer numerous health benefits, including improved gut health and antioxidant activity. Unfortunately, the processes used to isolate these carbohydrates are expensive; thus, the purpose of this research was to use high temperature processing obtain these compounds without the use of costly enzymes or chemicals. Optimum conditions for the release of AXOS from wheat bran included heating the wheat bran in water to 130 °C, washing the insoluble material, and then re-heating the wheat bran to 200 °C. This resulted in a 63.4% yield of AXOS, which is substantially higher than enzyme-based methods, which yield 30-40% of AXOS. This information will be useful for manufacturers of wheat products for increasing the value of their milling byproducts. Furthermore, consumers may benefit from the addition of AXOS to food products through improved gut health.

Technical Abstract:
The purpose of this research was to use two-stage hydrothermal processing to obtain feruloylated arabinoxylooligosaccharides (AXOS) from wheat bran without the use of enzymes or chemicals. In the first stage, wheat bran in water (10% w/w solids) was heated from room temperature (20 °C) to 130 °C at 10 °C/min in a special microwave oven that allowed for accurate control of temperature. This released 363 mg total solids, 169 mg starch, and 11.3 mg of arabinoxylan per g of wheat bran (dry matter). Following this hydrothermal pretreatment, wheat bran was again heated under the same conditions as above to final temperatures of 170 to 220 °C to induce autohydrolysis. Final temperatures of 200 and 210 °C released the most AXOS (117 and 114 mg/g wheat bran) and esterified ferulate (1.65 and 1.74 mg/g wheat bran). This represented about 60 and 30% of the starting arabinoxylan and ferulic acid contents, respectively. Treatment to 200 °C was selected as the optimum treatment temperature over 210 °C because autohydrolysate liquors contained lower concentrations of many contaminants, including non-starch glucan, free sugars, and furfural, and treatment to 200 °C retained a higher proportion of high molecular weight (>1,338) compounds than 210 °C.